High frequency communicating system



K. E. HASSEL. 2,021,060

HIGH FREQUENCY COMMUNICATING SYSTEM Filed June 9, 1924 Nov. 12, 1935.

2 Sheets-Sheet l LG 3 W jive nfor Karl Ehasse] Al I N 1935. K. E. HASSEL HIGH FREQUENCY COMMUNICATING SYSTEM Filed Ju ne 9, 1924 2 Sheets-Sheet 2 Inventor. Karl E. Has sel Patented Nov. 12, 1935 UNITED STATES PATENT OFFICE HIGH FREQUENCY COMBTUNICATING SYSTEM corporation of Illinois Application June 9, 1924, Serial No. 718,740

25 Claims.

This invention relates to the control of the transfer of energy in communicating systems depending upon high frequency currents for their operation, and it has to do more particularly with the regulation of current flow in radio or high frequency receiving systems.

In such systems the received energy, whether it is guided to the receiving station over wires or whether it is generated in a receiving antenna or collector by electromagnetic waves transmitted through the ether, is of extremely small amplitude and ordinarily must have its amplitude greatly increased in order that the energy may be of such magnitude as to operate the receiving apparatus satisfactorily. The present invention has primarily to do with securing uniform amplification throughout a considerable range of wave lengths of the energy received from distant stations while at the same time maintaining a high degree of selectivity or discrimination between the waves of transmitting stations simultaneously operating at slightly different frequencies, and to secure these results with the greatest possible ease of control of the wave selecting or tuning apparatus at the receiving station.

Where the receiving circuit includes one or more stages of radio frequency amplification with tuning apparatus associated with each stage for tuning that stage to the frequency of the particular wave that it is desired to receive, the degree of amplification obtained is not uniform throughout the wave length range, but varies considerably for the various frequencies. One of the factors which enters into the amount of amplification obtained is the nature and degree of coupling between the various stages. For each wave length there is a definite degree of coupling that gives the maximum degree of desirable amplification, and in order that the amplification may be maintained ata uniformly high value for each of the wave lengths within the tuning range of the apparatus, it has been found that there should be a corresponding change in the degree of coupling from one wave length to the other between each stage and the next in the series. In investigating the matter I have discovered that it is possible by designing and relating the circuits and apparatus in accordance with the manner hereinafter disclosed so to coordinate the wave length tuning adjustment of each stage with the coupling between that stage and the preceding stage that it is possible to secure approximately maximum amplification of uniform value throughout the tuning range of the apparatus. This principle of automatic coordination between wave length tuning and degree of coupling between the tuned circuit and other circuits operatively related with the system is capable of application in a variety of different ways to the securing of equalization of energy transfer be- 5 tween different parts of the receiving circuit.

In the following the manner in which this principle is applied in a preferred embodiment of one of the various applications of the invention possible will be described by reference to the drawings 10 in which Fig. 1 represents the circuit of a tuned radio frequency receiving circuit in which the transfer of energy from one stage to another is equalized in accordance with my invention; Fig.

2 illustrates a potentiometer control of one of the 15 stages of amplification for checking up on the energy equalization for different wave lengths; Fig. 3 is a plan view of one form of energy equalizing control unit which I have found suitable for accomplishing the purposes of the invention; 20 and Figs. 4 and 5 are detailed views of portions of the control unit.

In Fig. 1, which shows one of the high frequency receiving circuits in which my invention may advantageously be employed, the antenna 25 or collector 9 is coupled by means of a transformer ID with the input circuit of the thermionic valve 4, the primary winding ll of the transformer being included in the antenna circuit and the secondary winding l2 forming with the vari 30 able condenser IS a resonant circuit the terminals of which are connected with the grid and filament of amplifier M. The output circuit of the amplifier l4 includes serially the B battery and the turns 2| and 22 constituting the primary winding of the radio frequency transformer 20. The primary winding 2|, 22 is electro-magnetically coupled with a resonant circuit comprising the secondary winding 23 and shunted variable condenser 25, the terminals of this resonant circuit being connected respectively with the grid and filament of the thermionic amplifier 24 to constitute the input circuit of the amplifier. The output circuit of the amplifier 24 includes serially 4 the battery B and the turns 3| and 32 of the radio frequency transformer 30, the output circuit being completely by way of the plate and filament of the amplifier 24. The primary winding 3|, 32 of the radio frequency transformer 30 is electro-magnetically coupled with the resonant circuit including the secondary winding 33 of the transformer and the shunted variable condenser 35. The terminals of the last mentioned resonant circuit have connection with the filament of the thermionic detector tube 34 and also with the grid of the detector 34 by way of the usual condenser 36 and high resistance leakage path 31'. The output circuit of the detector 34 includes the battery B and the telephone receivers 39, the usual by-pass condenser 38 being shunted about the telephone receivers. The filaments of the thermionic valves or tubes l4, 24 and 34 are heated by means of the batteries A, A and A These batteries, as well as the plate circuit batteries B, B and B for clearness in illustration are shown as separate batteries in the drawings; but it will be understood that a single A battery and a single string of B battery cells may supply the filament current and the plate or space current to the appropriate parts of the circuit in accordance with the usual practice.

In the circuit described above the transformer l6 which couples the antenna with the input circuit of the first amplifier tube |4 may be an ordinary air core radio frequency transformer, the

turn ratio and the coupling between the primary winding H and the secondary winding I2 being such that the antenna circuit is substantially an untuned circuit the energy in which is transferred to the input circuit of the tube l4 through the medium of the associated resonant circuit which may be tuned to any desired frequency by means of the variable condenser I5.

The transformer 20 which couples the output circuit of the amplifier tube M with the amplifier tube 24, and the transformer which couples the output circuit of the amplifier tube 24 with the detector tube 34 are, however, specially constructed and related with the respectively associated variable condensers 25 and 35 to constitute high frequency controlling units adapted for the equalization of energy transfer in accordance with the principles of my invention. One of the forms in which such a control unit may be built, and a form which I have found gives good results in practice, is illustrated in Figs. 3, 4 and 5 of the drawings. Referring to these figures, is a metal frame variable condenser the movable element or rotatable plates of which are mechanically connected, in the present instance by means of the rotatable shaft 4|, with a movable element 42 of the radio frequency transformer 43. The frame of the variable condenser 40 may be secured to the panel 44 by means of the posts 45 that project from the front plate of the condenser frame. The variable condenser 40 may comprise the usual combination of a plurality of fixed or stationary plates 46 interleaved with a plurality of rotatable plates 41. The rotatable plates are rigidly secured to the rotatable shaft 4|. The rotatable shaft 4| and its plates 41 are in metallic connection with the metallic frame of the condenser, while the fixed or stationary plates 46 are rigidly attached to metallic posts 48 which are carried upon a transverse insulating block 49 se cured to the frame of the condenser, the fixed plates thus being insulated from the movable plates. Electrical connection with the rotatable plates is by way of the connecting terminal 50 and electrical connection with the fixed plates is by way of the terminal 5|.

The transformer or electro-magnetic coupling element of the controlling unit includes a tube of insulating material 52 upon the outside of which is placed the secondary winding 53, which in the specific embodiment illustrated consists of sixty turns of wire half of which are Wound on one end of the tube and the other half on the other end of the tube. A strip of insulating material 54 is placed over the center of one half of the secondary winding 53, and upon this insulating strip is placed a portion 55 of the turns of the primary winding. These turns in the present instance are illustrated as being five in numher. The remaining turns 56 of the primary winding, which in the present instance are illustrated as being six in number, are placed upon the movable or rotating element 42 of the transformer, being shown as divided and three turns placed upon each end of the movable member. The turns 56 constitute a continuous winding, and are connected in series with the turns constituting the stationary portion 55 of the primary winding.

The movable element or member 42 is formed of a ring or short tube of insulating material concentric with and Within the stationary tube of the transformer. It is rigidly fixed, in the present instance, to the inner end of the shaft 4| upon which the rotatable plates of the condenser are mounted by means of a bracket 51, the separation between the fixed and rotating elements of the transformer being just sufficient to allow clearance as the movable member is rotated. The forward end of the shaft 4| projects through the panel 44 and is provided with a knob 58 by means of which the shaft may be rotated. As the shaft 4| is turned by means of the knob, the movable elements of both the variable condenser 40 and the transformer 43 are simultaneously rotated with respect to the fixed elements, the outer shell or insulating tube 52 of the transformer being held stationary by being attached to the frame of the condenser by means of the bracket 59.

For use in the circuit illustrated in Fig. l of the drawings, the rotatable element or member 42 of the transformer is fixed upon the rotatable shaft 4| 0f the variable condenser in such a way that when the movable plates of the condenser are entirely included between the fixed plates to give maximum capacity value, the portion 56 of the primary winding on the rotatable member 42 has its turns in the same direction as the turns in the stationary portion 55 of the primary winding, the electro-magnetic effect of the primary turns therefore being additive, the magnetic axes of the three windings coinciding, and the electro-magnetic coupling of the primary and secondary windings of the transformer therefore being at its maximum. As the rotatable shaft 4 4| is rotated to separate the movable plates from the fixed plates of the condenser, the portion 56 of the primary winding upon the rotatable member 42 has its electro-magnetic relation with the fixed portion 55 of the primary winding and the fixed secondary winding 53 correspondingly changed, with a corresponding shifting of the magnetic axis of the resultant primary field with relation to the magnetic axis of the secondary field, and when the rotatable shaft has been turned through an angle of 180 degrees to completely separate the movable from the fixed plates of the condenser, the magnetic effects of the movable and fixed portions of the primary winding of the transformer are in opposition with respect to each other, the magnetic axes of the primary and secondary systems are at the widest angle with relation to each other, and the electromagnetic coupling between the primary and secondary windings of the transformer is at its minimum.

In order that the change in the transformer coupling may take place at a rate that permits the desired relation between transformer coupling and condenser capacity to be obtained at all tuning adjustments with direct mechanical connection between the movable elements of the condenser and transformer, it has been found desirable to employ a ratio of primary turns to secondary turns approximately as illustrated in this specific embodiment of the invention, and preferably to split the primary winding and ar range part of the turns with a fixed and part with a movable relation to the secondary winding. It will be understood however that the turn ratio between the primary and secondary windlugs and the ratio of movable to fixed turns in the primary winding, as well as the normal separation between secondary turns and fixed or movable primary turns is subject to variation in different embodiments of the invention, and may readily be determined for the particular use in which the invention is desired to be employed.

Referring now to the actions which take place when the invention is used in a circuit such as that illustrated'in Fig. 1, the receiving circuit is tuned for the selective reception of the desired wave length in the broadcast range by the adjustment of the variable condensers I5, 25 and 35 to make resonant to that particular wave length the resonant circuits of which the condensers I5, 25 and 35 form a part. The tendency for the transfer of energy between each of the resonant circuits 25, 23 and 35, 33 and the windings 2|, 22 and 3|, 32 in the preceding output circuit to which the corresponding resonant circuit is coupled, increases with the rise in frequency and corresponding reduction in wave length. But, as has been described, the coupling between the windings 2|, 22 and 23 and between the windings 3|, 32 and 33 is not a fixed coupling, but is a coupling that is continuously varied in degree with the variation in the tuning of the condensers 25 and 35 of the associated resonant circuits; and, as has been described, the relationship is such that as the plates of the tuning condenser are turned to increase the capacity and make the circuit resonant to a longer wave length, with a consequently diminished tendency for energy transfer through the coupling, the coupling is tightened by the simultaneous turning of the movable portion 22 or 32 of the primary transformer winding to compensate for the diminished tendency for energy transfer between the coupled elements of the circuit. The energy transfer relationship between the coupled elements is thus maintained at a substantially uniform value for obtaining maximum amplification throughout the entire wave length range for which the organization is designed without imparting the resonance characteristics of each resonant circuit to an undesirable extent to the associated coupled output circuit. The coordinate relationship between the tuning adjustment and the coupling adjustment is indicated in each of the controlling units of the circuit of Fig. 1 where this relationship exists byv means of the diagonal arrow which is drawn through the transformer windings 22 and 23 and the variable condenser 25 in the one case, and through the transformer windings 32 and 33 and the variable condenser 35 in the other case.

As a convenient means for checking the uniformity of maximum amplification throughout the entire wave length range, I have found it convenient to associate a potentiometer with the grid or input circuit of the amplifier 24. This potentiometer 26 is shown in Fig. 2 of the drawings. By the variation of potential which it is possible to impose upon the grid of the amplifier by means of the potentiometer 26, it is possible to effect a uniform adjustment of the energy transfer equalizing means at a point where the amplification is at its maximum and distortion is absent throughout the entire wave length range.

In the radio frequency amplifying system in connection with which the invention is disclosed, in the particular embodiment illustrated in Fig. 1, it is desirable to avoid electro-magnetic coupling between the transformers in the different stages such as takes place through the medium of the leakage lines of force. This-may be accomplished in any convenient and well known way, such as by shielding or by so arranging the transformers that their axes are at right angles to each other. The latter is the method which is employed in the particular embodiment of the invention of which Fig. 1 is a diagrammatic illustration, the tubes or shells upon which the secondary windings 53 of the transformers as illustrated in Figs. 3, 4 and 5 are wound being readily turned into a right angle relation with each other by turning the supporting bracket 59 upon the sleeve surrounding the rotatable shaft 4| and locking it in its position of adjustment by means of the associated lock nut, the setting of the rotatable member of the transformer being correspondingly changed upon the rotatable shaft 4|. The secondary winding of the transformer Ill may be mounted With its axis horizontal, which brings all of the transformers into a right angle relation with each other.

What is claimed is: g

l. A high frequency controlling unit comprising a variable condenser and a transformer adjustably supported on the frame of said condenser and having windings relatively movable with respect to each other, and a mechanical connection between the rotatable elements of the condenser and one of the transformer windings for simultaneously varying the adjustment of the same.

2. A high frequency controlling unit comprising a variable condenser and a transformer each having a stationary element and a movable element, means for adjustably mounting the stationary and movable elements of one respectively 4 upon the stationary and movable elements of the other, and means for simultaneously varying the position of the movable elements of said condenser and said transformer with respect to the stationary elements thereof.

3. A high frequency controlling unit comprising a variable condenser and a transformer hav ing a secondary winding interposed between a stationary portion and a movable portion of the associated primary winding and in fixed relation to said stationary portion, and means for moving the movable element of said variable condenser and simultaneously moving the movable portion of the primary winding of said transformer.

4. A high frequency controlling unit comprising a variable condenser and a transformer having a portion of one of its windings stationary and concentric and another portion movable with respect to the other winding in order to vary the coupling thereof, and means for moving the movable element of said variable condenser and simultaneously moving the movable portion of the aforesaid transformer winding.

5. A high frequency controlling unit compris ing a variable condenser and a transformer having a stationary secondary winding connected with the terminals of said condenser to constitute a resonant circuit, a primary winding for said transformer having a portion of its turns movable with respect to said secondary winding to vary the coupling therebetween, and means for simultaneously moving the movable element of said condenser and tr e movable portion of said primary winding to vary the coupling of said transformer windings in accordance with the variation in tuning of said resonant circuit.

6. An electrical network including a thermionic valve having an input circuit and an output circuit, a resonant circuit including means for tuning the same and means for inductively coupling the same with said output circuit independently of said tuning means, and means for simultaneously varying said tuning means and coupling means to vary the degree of coupling between said output circuit and said input circuit in the tuning of the latter.

7. An electrical network including a thermionic valve having a resonant input circuit and an output circuit, a resonant circuit including a variable condenser for tuning the same and an inductance element, means for electro-magnetically coupling said output circuit with said last mentioned resonant circuit through the medium of the inductance elem nt thereof, and means for simultaneously to g said last mentioned resonant circuit to the frequency of said resonant input circuit and correspondingly varying the degree of the electro-magnetic coupling between said output circuit and the associated resonant circuit.

8. An electrical network including a thermionic Valve having an input circuit and an output circuit, a resonant circuit, a variable condenser for tuning the same, a transformer coupling between said output circuit and said resonant circuit, and means for actuating said variable condenser to change the tuning of said resonant circuit and simultaneously varying the transformer coupling between said resonant circuit and said output circuit by shifting the magnetic axes of the transformer elements with relation to each other.

9. In a radio frequency receiving system, a therminoic amplifier having a tuned input circuit and an untuned output circuit, an adjustable resonant circuit including a variable condenser for controlling the tuning thereof, an adjustable transformer coupling between said resonant circuit and said untuned output circuit, and means for changing the value of said transformer coupling in accordance with the tuning of said resonant circuit.

10. An electrical network including a thermionic valve having an input circuit and an output circuit, a resonant circuit including a variable condenser for tuning the same to various wave lengths, adjustable coupling means between said resonant circuit and said output circuit, and means operating automatically to loosen or tighten the coupling as said esonant circuit is tuned for shorter or longer wave lengths respectively.

11. A radio frequency receiving system including a thermionic amplifier having a tuned input circuit and an output circuit, a resonant circuit including a variable capacity element and a substantially unvarying self inductance element, a coupling coil of relatively low self inductance included in said output circuit and in variable coupling relation with the self inductance element of said resonant circuit, and means for actuating said variable capacity element to tune the resonant circuit and acting simultaneously to vary the coupling relation of said coupling coil, said means operating to tighten the coupling in tuning for longer wave lengths and to loosen the coupling in tuning for shorter wave lengths.

12. In a radio frequency receiving system including a plurality of amplifying stages, each amplifying stage including a thermionic valve, a resonant circuit included in the input circuit of each thermionic valve, each resonant circuit including a variable capacity element and a substantially unvarying self inductance element, a coupling coil of relatively low self inductance included in the output circuit of the thermionic valve of one stage and in variable coupling relation with the self inductance element of the resonant circuit of the next stage, and means for coordinately adjusting the variable capacity element and the associated coupling coil of the resonant circuit to tighten the coupling as the resonant circuit is adjusted for longer wave lengths and to loosen the coupling as the resonant circuit is adjusted for shorter wave lengths.

13. A radio communicating system including a plurality of amplifying stages, transformers coupling said stages, each transformer including a secondary winding of relatively high and unvarying self inductance and a primary winding of relatively low self inductance arranged in variable coupling relation with the associated secondary winding, said transformers being so mounted as substantially to prevent strayfield coupling between the same, a variable condenser for each of said amplifying stages, each condenser being connected with the secondary winding of the associated. transformer to constitute a. resonant circuit, and means for coordinately adjusting each variable condenser and the coupling relation of the primary winding of the associated transformer to tighten the coupling when the resonant circuit is tuned for longer wave lengths and to loosen the coupling when the resonant circuit is tuned for shorter wave wengths.

14. A radio communicating system including a plurality of amplifying stages, transformers coupling said stages, each transformer having a fixed secondary winding of relatively high self inductance and a movable primary winding of relatively low self inductance, said transformers being so mounted as substantially to prevent stray field coupling, a variable condenser connected with each secondary winding to constitute therewith a resonant circuit, and means for coordinately actuating each variable condenser and the movable primary winding of the associated transformer to vary the coupling relation as the associated resonant circuit is tuned for longer or shorter wave lengths without substani tially shifting in space the stray field of the associated secondary winding.

15. A high frequency controlling unit comprising a variable condenser and a coupling transformer having two windings, one of said windings and a portion of said other winding being arranged in fixed relation with each other, and the remaining portion of said other winding being movable relatively thereto, and a mechanical connection between the rotatable plates of the variable condenser and the movable portion of said other winding.

16. In a multi-stage transformer coupled, radio frequency system, means for varying the capacity in each transformer secondary circuit, means for varying the self-inductance of each primary and the mutual inductance of each transformer, and means for mechanically coupling said first named means with said second named means to thereby vary said capacity, said self-inductance and said mutual inductance simultaneously and in the same direction, said coils and said condensers being relatively so proportioned that objectionable feed-back oscillations are substantially eliminated.

17. In a multi-stage transformer coupled, radio frequency system, each transformer comprising relatively fixed primary and secondary coil portions, each primary further including a relatively movable coil portion, a tuning condenser connected across the secondary of each radio frequency stage, and means for mechanically coupling each movable primary coil portion with its associated tuning condenser to thereby vary the self inductance of each primary and the mutual inductance of each transformer simultaneously with and in the same direction as the variation of the capacity of the associated tuning condenser, said coils and said condensers being relatively so proportioned that objectionable feed-back oscillations are substantially eliminated.

18. In a multi-stage transformer coupled, radio frequency system, each transformer comprising relatively fixed primary and secondary coil portions, each primary further including a relatively movable coil.portion, a tuning condenser connected across the secondary of each radio frequency stage, and means for mounting each movable primary coil portion on the shaft of its associated tuning condenser to thereby vary the self-inductance of each primary and the mutual inductance of each transformer simultaneously with and in the same direction as the variation of the capacity of the associated tuning condenser, said coils and said condensers being relatively so proportioned that objectionable feed-back oscillations are substantially eliminated.

19. In a radio frequency tuner, a transformer having two primary coils and one secondary coil, a variable condenser for tuning said secondary coil, one of the primary coils being fixed in relation to said secondary coil, said condenser having a shaft and one of said primary coils being mounted upon the shaft of said variable condenser and rotatable therewith, said primary coils being so arranged and proportioned that both their self inductance and their mutual inductance with said secondary increases with the increase of the capacity of said condenser.

20. A radio frequency tuner comprising a condenser having a stator and a rotor, a frame supporting said parts, secondary coil supported by said frame and having its axis at an angle to the axis of said rotor, a primary coil coaxial with said secondary coil and supported by said frame, and a primary coil carried by and rotatable with said rotor.

21. A radio tuner comprising a condenser having a' stator, a rotor and a frame therefor, a

transformer comprising a stationary secondary coil, a primary coil coaxial therewith, a primary coil rotatably supported on an axis at approximately right angles to the axis of the other coils and connected to the rotor to rotate therewith.

22. A tuner comprising a transformer consisting of a relatively fixed secondary coil and a primary coil formed in two sections, one of which is relatively fixed with the secondary and the other of which is movable relative thereto, and a variable condenser having a stator and a rotor electrically connected with the secondary coil and means for mechanically coupling the rotor and the movable primary coil section so that they move together to simultaneously vary the inductance and capacity in the same direction.

23. A tuner comprising a variable condenser having stationary and movable elements, a transformer having two stationary coils and a movable coil, one of the stationary coils being electrically connected to the condenser, and means for mechanically coupling the movable coil with the movable element of the condenser so that the capacity of the condenser will increase simultaneously with the increase of the self-inductance and mutual inductance of said coils.

24. A radio frequency receiving system including a thermionic amplifier having a tuned input circuit and an output circuit, a resonant circuit including a variable capacity element and a substantially unvarying self-inductance element, a coupling coil included in said output circuit and in variable coupling relation with the self-inductance element of the said resonant circuit, and means for actuating said variable capacity element to tune the resonant circuit and acting simultaneously to vary the coupling relation of said coupling coil, said means operating to tighten the coupling in tuning for longer wave lengths and to loosen the coupling in tuning for shorter wave lengths.

25. In a radio frequency receiving system including a plurality of amplifying stages, each amplifying stage including a thermionic valve, a resonant circuit included in the input circuit of each thermionic valve, each resonant circuit including a variable capacity element and a substantially unvarying self-inductance element, a coupling coil included in the output circuit of the thermionic valve of one stage and in variable coupling relation with the self-inductance element of the resonant circuit of the next stage, and means for coordinately adjusting the variable capacity element and the associated coupling coil of the resonant circuit to tighten the coupling as the resonant circuit is adjusted for longer wave lengths and to loosen the coupling as the resonant circuit is adjusted for shorter wave lengths.

KARL E. HASSEL. 

